Specifically, though not exclusively, the invention is applicable to the field of rapid attachment apparatus for machines for moving materials, such as, for example, buckets fitted onto the extremities of tool arms on work machinery. Numerous rapid attachment devices are taught in the prior art, which are suitable for the purpose but which are unable to solve definitively and satisfactorily the problem of automatic increase in play in the couplings between the parts, due to the not inconsiderable wear involved. The main aim of the present invention is to obviate the above-described limits in the prior art.